Transport Properites In Electrostatic-magnetically Modulated Graphene Monolayers

Graphene is a rising star in the fields of condensed matter physics and materialscience in the recent years. It is a strictly 2D crystal combined from carbon atoms,which reveals great potential in electronic engineering applications. Moreover,its Diraclike energy spectrum make it a perfect analogue of QED theory in thescope of CMP. In this thesis, the transport properties of magnetically modulatedgraphene are studied using the transfer matrix technique. The strength and theconfigurations of the external magnetic and electrostatic modulation are taken intoconsideration. Main results are concluded as follows:1)The authors have investigated resonant tunneling in nonuniform magnet-ically modulated graphene-based double-barrier structures, which can be realizedexperimentally by depositing successive ferromagnetic stripes on graphene mono-layer. The e?ects of Klein tunneling, resonant tunneling, and magnetically inducedwave vector filtering on the shot noise are taken into consideration. It is foundthat the shot noise is enormously enhanced in antiparallel magnetization align-ment, and striking Poissonian value plateaus of the Fano factor can be formed,which is dramatically distinguishable from that in parallel alignment. The resultsindicate that the shot noise could be a sensitive probe to reveal mechanism ofelectronic transport in graphene.2)The authors have investigated the dwell time of electrons tunneling throughnonuniform magnetically modulated graphene monolayer. Two types of models,i.e., the square magnetic barrier and theδ-function magnetic barrier, are intro-duced to simulate the magnetic modulation realized by depositing nanoscale ferro-magnetic stripes on top of the graphene monolayer. It is found that both the dwelltime and the transmission probability show remarkable anisotropy that varies indi?erent magnetically modulated configurations. Particularly, when the electronstunnel through the graphene monolayer modulated by two antiparallelly alignedferromagnetic stripes, the corresponding transmission probability exhibits angu-larly symmetric property, whereas the dwell time does not. Moreover, there existsgreat discrepancy of the dwell time between in the Klein tunneling region andin the resonant tunneling region, where each region corresponds to the perfect transmission peaks.